This invention relates to a current detector for detection or measurement of electric current flowing in an electric circuit, and more specifically to such a detector incorporating a Hall-effect device more generally known also as Hall generator.
The Hall generator is built upon the familiar Hall effect to develop a voltage, known as Hall voltage, in proportion to the strength of the magnetic field applied. The Hall generator therefore lends itself to use as a magnetism detector. Additionally, positioned contiguous to a path of electric current, the Hall generator will put out a voltage indicative of the magnitude of the current by being acted upon by the magnetic field appearing in proportion to the current magnitude. The closer the Hall generator is positioned to the current path, the higher will be its sensitivity of current detection.
The instant applicant proposed in Japanese Unexamined Patent Publication No. 2000-174357 a current detector employing a Hal generator. This prior art device was designed explicitly for high detection sensitivity. To this end a current-path conductor layer for the flow of electric current to be detected was laid, via an insulating film, over a semiconductor substrate having a Hall generator formed therein. The prior art device has later proved to have some shortcomings.
The first of such shortcomings arises from the fact that the prior art current detector had to be wholly enveloped in a unitary encapsulation by reason of its very construction. The integral construction, from an early stage of manufacture, of the current-path conductor and the Hall generator is objectionable because the complete device has to be discarded for a defect associated with either the current-path conductor and the Hall generator, resulting in low productivity per unit of effort. A drastic increase in productivity is certain to occur if the current-path conductor and the Hall generator are manufactured in separate assemblies that can be put together in the final stage of manufacture.
Another weakness is the difficulty of assuring consistently high sensitivity and reliability for all the models manufactured. This difficulty has been found attributable to the fact that the positional relationship between the current-path conductor and the Hall generator is prone to fluctuation from model to model. Additionally, the conductor layer of the prior art device could tolerate current of only 10 amperes or so. There has therefore been awaited the advent of a device that can be put to use for detection of current of much greater magnitude, 100 to 600 amperes for instance, without sacrifice in sensitivity or in immunity to noise.